Population Viability Analysis of the Endangered Shortnose Sturgeon (Acipenser brevirostrum)

SUSTAINABLE INFRASTRUCTURESI-1543

Background:Rivers
and estuaries along the Atlantic coast support both military
installations and populations of the federally endangered shortnose
sturgeon (Acipenser brevirostrum). This project will focus on the
population in the Ogeechee River system, near Fort Stewart. Potential
factors that threaten recovery of this population include: (1) siltation of spawning areas, (2) degraded water quality in summer due to upstream agriculture, urban development, and military land use,
(3) atmospheric mercury, (4) saline water introduced through rice canals, and (5)
by-catch in the shad fishery. Each of these factors influences one or
more lifestages through the following mechanisms: (a) siltation of
spawning gravels, (b) methyl mercury toxicity to early lifestages, (c)
salinization of freshwater habitat, (d) degraded summer water quality,
and (e) harvest. Military land and water management practices influence
some of these factors because rivers collect and concentrate the
effects of land disturbances, and because installations
discharge wastewater.

Objective:The
goals of this research are to: (1) quantitatively partition the
influences on shortnose sturgeon recovery under the control of the
military from those that are not, (2) prioritize recovery efforts, and
(3) quantify population thresholds. Through modeling efforts, this
project aims to quantify the cumulative and separate effects of: (1)
siltation, (2) nutrient and carbon inputs to rivers due
to military activities and land management, (3) atmospheric mercury, (4) rice canal salt inputs, and (5) by-catch in
the shad fishery, on the long-term persistence of the shortnose
sturgeon population in the Ogeechee River, and the Canoochee River which drains Fort Stewart, Georgia.
Through additional empirical research, this project aims to improve the
understanding of stressors affecting blackwater rivers and the fish
that populate them.

Summary of Process/Technology:Population
viability analysis (PVA) provides a scientific basis for assessing
cumulative and separate effects through a combination of empirical
analysis and modeling. Mechanistic PVA models make it possible to
partition the influences of contributing recovery factors, with the
goal of prioritizing recovery efforts. A coordinated field and modeling
effort will be conducted in order to quantify cumulative effects on the
endangered shortnose sturgeon at Fort Stewart. A mechanistic, spatial
PVA model will be designed and implemented that links sturgeon
population dynamics to land and water uses on- and off-base. These
linkages will depend on modeling the physical habitat and developing
empirical relationships between the river habitat and individual
sturgeon growth, survival, and reproduction. These relationships will
be obtained by analyzing existing data and collecting new data to fill
critical information gaps. The importance of each sturgeon recovery
factor will be estimated by comparing the distributions of population
sizes predicted by a series of model simulations where one or more risk
factor is removed from the model.

Benefit:A
mechanistic PVA modeling approach will be developed for predicting how
on-base and off-base uses of land and water modify the habitat and
water quality experienced by a riverine fish. The results will have
direct relevance to prioritizing recovery efforts for southern
populations of shortnose, Gulf, and Atlantic sturgeon, all of which are
species of conservation concern.

Accomplishments:This is a FY07 New Start Project. Accomplishments will be listed upon its completion.